A known machine of the general type to which the invention relates includes a housing having angular channels therein and a fixed commutator within the housing, the commutator having a sequence of control openings circularly and uniformly spaced around the commutator to convey fluids between inlet and outlet ports and rotatable working chambers and a control plate coupled to the output shaft. The commutator has alternating passages which provide radial fluid flow to one of two possible annular grooves or channels and also has axial passages leading to the control plate. As will be recognized by those skilled in the manufacture of devices of this type, creating a commutator member having the variously shaped control channels and large passage cross-section presents significant manufacturing difficulties. If the commutator is manufactured from a sintered material, then it is necessary to accomplish a supplemental mechanical manufacturing step which is quite expensive. An apparatus of this type is shown in publication RE14325/12.80 of Mannesmann-Rexroth, a corporation of Lohr-Main, West Germany, the contents of which are incorporated herein by reference.